Validation, method quantitative analysis

Like all classical quantitative analysis methods, NMR spectroscopy needs calibration, calibration standards and a validation procedure. The standard techniques are used for calibration external calibration, the standard addition method and the internal standard method. A fourth is a special NMR calibration method, the tube-in-tube technique. A small glass tube (capillary) containing a defined amount of standard is put into the normal, larger NMR tube filled with the sample for analysis. In most cases, there are slight differences in the chemical shift of corresponding signals of the same molecule in the inner... 

Cordero C, Bicchi C, Joulain D, Rubiolo P (2007) Identification, quantitation and method validation for the analysis of suspected allergens in fragrances by comprehensive two-dimensional gas chromatography coupled with quadrupole mass spectrometry and with flame ionization detection. J Chromatogr A 1150 37-49... 

Quantitative Analysis for a Single Analyte The concentration of a single analyte is determined by measuring the absorbance of the sample and applying Beer s law (equation 10.5) using any of the standardization methods described in Chapter 5. The most common methods are the normal calibration curve and the method of standard additions. Single-point standardizations also can be used, provided that the validity of Beer s law has been demonstrated. 

HPLC coupled with an evaporative light scattering (ELS) detector has been used as an universal detection technique also valid for quantitative analysis. Alcohol ether sulfates were analyzed by this method with good results and also at very low concentrations [295]. 

Method validation is needed to demonstrate the acceptability of the analytical method. A recovery test on a chemical being determined should be performed in order to verify the reliability of the series of analyses. Recovery studies are usually conducted by spiking untreated sediment with the target chemical at the deteetion limit, quantitation limit and in the range of 10-50 times the detection limit. The method is considered acceptable when the recoveries typically are greater than 70%. When the recovery is less than 70%, an improvement in the analytical methods is needed. Where this is not possible for technical reasons, then lower recovery levels may be acceptable provided that method validation has demonstrated that reproducible recoveries are obtained at a lower level of recovery. Analysis is usually done in duplicate or more, and the coefficient of variation (CV) should be less than 10% to ensure that recoveries will be consistently within the range 70-110%. 

On-line SFE-SFC method development for validated quantitative analysis of PP/(Irganox 1010/1076, Tinuvin 327) has been reported [93]. SFE conditions required optimisation of extraction time and pressure, matrix type (particle or film) and matrix parameters (particle size, film thickness, sample weight). About 30% of extracts were lost during collection. Very poor recoveries (20-25 %) were reported from ground samples (particle size 100 p,m dependent recoveries of 45-70% for 30-p.m-thick films. Biicherl... 

De Lean, A., Hancock, A. A. and Lefkowitz, R. J. (1982). Validation and statistical analysis of a computer modeling method for quantitative analysis of radioligand binding data for mixtures of pharmacological receptor subtypes, Mol. Pharmacol., 21, 5-16. 

To develop a validated method for the quantitative analysis of Class IV caramels in soft drinks. 

Numerous CE separations have been published for synthetic colours, sweeteners and preservatives (Frazier et al., 2000a Sadecka and Polonsky, 2000 Frazier et al., 2000b). A rapid CZE separation with diode array detection for six common synthetic food dyes in beverages, jellies and symps was described by Perez-Urquiza and Beltran (2000). Kuo et al. (1998) separated eight colours within 10 minutes using a pH 9.5 borax-NaOH buffer containing 5 mM /3-cyclodextrin. This latter method was suitable for separation of synthetic food colours in ice-cream bars and fmit soda drinks with very limited sample preparation. However the procedure was not validated for quantitative analysis. A review of natural colours and pigments analysis was made by Watanabe and Terabe (2000). Da Costa et al. (2000) reviewed the analysis of anthocyanin colours by CE and HPLC but concluded that the latter technique is more robust and applicable to complex sample types. Caramel type IV in soft drinks was identified and quantified by CE (Royle et al., 1998). 

There is a recent trend towards simultaneous CE separations of several classes of food additives. This has so far been applied to soft drinks and preserved fruits, but could also be used for other food products. An MEKC method was published (Lin et al., 2000) for simultaneous separation of intense sweeteners (dulcin, aspartame, saccharin and acesulfame K) and some preservatives (sorbic and benzoic acids, sodium dehydroacetate, methyl-, ethyl-, propyl- and isopropyl- p-hydroxybenzoates) in preserved fruits. Ion pair extraction and SPE cleanup were used prior to CE analysis. The average recovery of these various additives was 90% with good within-laboratory reproducibility of results. Another procedure was described by Frazier et al. (2000b) for separation of intense sweeteners, preservatives and colours as well as caffeine and caramel in soft drinks. Using the MEKC mode, separation was obtained in 15 min. The aqueous phase was 20 mM carbonate buffer at pH 9.5 and the micellar phase was 62 mM sodium dodecyl sulphate. A diode array detector was used for quantification in the range 190-600 nm, and limits of quantification of 0.01 mg/1 per analyte were reported. The authors observed that their procedure requires further validation for quantitative analysis. 

Part—I has three chapters that exclusively deal with General Aspects of pharmaceutical analysis. Chapter 1 focuses on the pharmaceutical chemicals and their respective purity and management. Critical information with regard to description of the finished product, sampling procedures, bioavailability, identification tests, physical constants and miscellaneous characteristics, such as ash values, loss on drying, clarity and color of solution, specific tests, limit tests of metallic and non-metallic impurities, limits of moisture content, volatile and non-volatile matter and lastly residue on ignition have also been dealt with. Each section provides adequate procedural details supported by ample typical examples from the Official Compendia. Chapter 2 embraces the theory and technique of quantitative analysis with specific emphasis on volumetric analysis, volumetric apparatus, their specifications, standardization and utility. It also includes biomedical analytical chemistry, colorimetric assays, theory and assay of biochemicals, such as urea, bilirubin, cholesterol and enzymatic assays, such as alkaline phosphatase, lactate dehydrogenase, salient features of radioimmunoassay and automated methods of chemical analysis. Chapter 3 provides special emphasis on errors in pharmaceutical analysis and their statistical validation. The first aspect is related to errors in pharmaceutical analysis and embodies classification of errors, accuracy, precision and makes... 

This 2D-method was validated for the concentration range between 0.005 and 0.5 pmol for D-amino acids and 0.05-5 pmol for L-amino acids. Within-day and interday precisions were always better than 8% relative standard deviation (RSD) and the accuracies for spiked rat plasma samples were between 95.5% and 100.2%. Limit of detections (LCDs) and limit of quantitations (LOQs) were reported to be as low as 3 fmol (S/N = 3-5 corresponding to 0.15 nmolg wet tissue) and 5 fmol (corresponding to 0.25 nmolg wet tissue). It was concluded that this assay is supposed to be one of the most sensitive analysis method for amino acid enantiomers in mammalian samples. 

Figure 5.1 shows the various characteristics and stages in a method validation program. For most quantitative methods of analysis, the method characteristics that require evaluation are accuracy, sensitivity, selectivity, precision and method limitations. Each of these characteristics have contributions from various effects, all of which require consideration within a method validation study. 

Wells, R. J. (1998), Validation requirements for chemical methods in quantitative analysis—Horses for courses Accred. Qual. Assur., 3,189-193. 

Internal standard (IS) calibration requires ratioing of an analytical signal to an IS which has very similar characteristics to that of the analyte of interest (an element which is similar to the analyte either in mass, ionisation potential or chemical behaviour). Quantitative analysis applying internal standardisation is the most popular calibration strategy in ICP-MS, as improvements in precision are obtained when the technique is appropriately used. Of course, the validity of this calibration method requires that one ensures a good selection of the correct internal standard. For this purpose it is possible to resort to chemometric methods [16]. 

Jemal, M., and Xia, Y. Q. (2000). Bioanalytical method validation design for the simultaneous quantitation of analytes that may undergo interconversion during analysis. J. Pharm. Biomed. Anal. 22 813-827. 

Using the calculational method based on DDFT, deviations from the cylinder bulk morphology have been identified as surface reconstructions [58, 62], The constructed structure or phase diagrams allowed surface field and confinement effects to be distinguished [57-59, 107, 145, 186], The comparative analysis of defect types and dynamics disclosed annihilation pathways via temporal phase transitions [36, 111]. Further, a quantitative analysis of defect motion led to an estimate of the interfacial energy between the cylinder and the PL phases [117]. A DDFT-based model was effectively used to simulate a block copolymer film with a free surface and to study the dynamics of terrace development [41,42], We showed how our computational method and an advanced dynamic SFM can be exploited in a synergetic fashion to extend the information about the elementary steps in structural transitions at the mesoscopic level. In particular, the experiments validate the dynamic DDFT method, and the DDFT calculations rationalize the characterization of the film surface in the interior of the film [187],... 

Agbaba et al. [56] developed an HPTLC method for the determination of omeprazole, pantoprazole, and their impurities omeprazole sulfone and N-methylpantoprazole in pharmaceutical. The mobile phase chloroform-2-propanol 25% ammonia-acetonitrile (10.8 1.2 0.3 4), enables good resolution of large excesses of the drugs from the possible impurities. Regression coefficients (r > 0.998), recovery (90.7-120.0%), and detection limit (0.025-0.05%) were validated and found to be satisfactory. The method is convenient for quantitative analysis and purity control of the compounds. 

Sample preparation in NLC and NCE is the most important step in analysis due to the nano nature of these modalities. The sampling should be carried out in such a way as to avoid changes in the chemical composition of the sample. The quantitative values of species depend on the strategy adopted in sample preparation. Extraction recoveries may vary from one species to another and they should, consequently, be assessed independently for each compound as well as for the compounds together. Materials with an integral analyte, that is, bound to the matrix in the same way as the unknown, which is preferably labeled (radioactive labeling) would be necessary, which is called method validation. As discussed above few papers described off- and online sample preparation methods on microfluidic devices. Of course, online methods are superior due to lower risk of contamination and error of methods. Not much work been carried out on online nanosample preparation devices, which need more research. Briefly, to get maximum extraction of analytes, sample preparation should be handled very carefully. 

Two important components of quantitative analysis of environmental samples are the determination of method detection limits and instrument calibration. Understanding how they contribute to data quality will enable us to make decisions related to data validity during the assessment phase of the data collection process. 

The absorption of pantoprazole at 295 nm was used for the quantitative determination, and the method validated and used for the analysis of pantoprazole in its tablets. The results of validation study indicated that the method is linear over the range of 1.0 to 3.0 mg/mL (r= 0.9999). The percent recovery and relative standard deviation were 99.3-101.5 (n=9), and less than 1.0%, respectively. This method can be used for quality control and routine analysis [5],... 

Deventer K, Delbeke FT (2003) Validation of a quantitative screening method for corticosteroids by liquid chromatography tandem mass spectrometry. In Shanzer W, GeyerH, Gotzmann A, Mareck U (eds) Recent advances in doping analysis, vol 11, Spert and Buch Straub, Koln,... 

---